An earth working machine typically utilizes a digging or cutting member which employs a plurality of shanks to which teeth are attached by a variety of means including welding, bolting, and wedge-fitting. It has been recognized that fastening provided by the combination of a holding clamp and tooth provides certain advantages over a sole boltless tooth fastened directly to a shank. These advantages stem from conflicting physical requirements of the cutting teeth and the holding mechanism. The cutting point of the tooth must be formed of a hard wear-resistant material while the holding mechanism usually requires a material of at least some elasticity and/or ductility. A sole boltless tooth cannot adequately fulfill both requirements.
As widely practiced in the art, a current boltless digging tooth connects to the snout of a shank by a wedging force between shank grooves and a receiving channel formed at one end of the tooth. Such an arrangement permits quick hammer-driven changing of worn teeth, as shown, for example, in U.S. Pat. No. 2,222,071 issued to Gustafson. The availability of rapid changing reduces costly down time, thereby permitting more economical operation of the equipment. A wedge coupling mechanism, however, requires a material having defined stress-strain characteristics, e.g., a certain amount of ductility or elasticity in the snout receiving channel of the tooth in order to permit adequate wedging engagement and resilient clamping force between the tooth and the shank to absorb impact forces under working load conditions, or to provide adequate clamping under conditions where centrifugal forces act to loosen the tooth. On the other hand, the cutting point of the tooth mandates use of an extremely hard wear-resistant material having de minimis flexural properties. Consequently, conventional boltless teeth must either be manufactured in two stages to achieve the opposing requirements of the cutting point and snout receiving channel of the tooth, which renders them expensive. Alternatively, if the tooth is made in one operational stage, the hardness-ductility parameters of the snout receiving channel and cutting point must be compromised, in which case the tooth quickly wears out, thus leading to more costly down time and tooth replacement cycles.
As also known, the cutting or digging member of an earth working machine is subjected to severe impact and abrasive forces. It very often happens that the tooth attachment system is also subjected to those same forces which impose mechanical deformations upon the attachment system. Such deformations, in turn, interpose difficulties in changing or adjusting worn cutting teeth thereby causing more costly down time. Moreover, impact forces induce vibrations which tend to loosen threaded fasteners.
It is also highly desireable to provide a holding clamp adapted for use with an "adjustable" cutting tooth so that a tooth having a worn tip might be quickly extended and refastened to the shank of the digging member. By adjustable, it is meant that the tooth may be loosened in the holding assembly, axially extended forward of the digging member of the earth working machine, and then refastened to the shank by the holding clamp. Provision of rapid adjustment provides substantial economic benefits in reduced machine down time and reduced teeth replacement costs since a substantial portion of the expensive tooth material may be consumed, rather than discarded. A tooth holding clamp utilizing fasteners such as bolts, dowel pins, screws or the like, such as shown by U.S. Pat. No. 3,750,761 to Smith et al., although adaptable for use with adjustable cutting teeth, suffers not only from the laborious slow-pace tooth changing or adjustment process, but also from mechanical deformation and loosening of the fastener heads occurring during digging or cutting operations.
U.S. Pat. No. 2,940,192 to Lattner and U.S. Pat. No. 4,576,239 to Launder show non-adjustable teeth-holding clamps which suffer, inter alia, from the lack of adjustability of the clamped position the cutting tooth relative to the shank, and thus will impose significant operating costs on the end user. Not only are their cutting teeth non-adjustable, which requires the discarding of a substantial amount of specially treated and formed hard wear-resistant material of the teeth, but their teeth have relatively complex physical dimensions which add to their cost of manufacture since they cannot be conveniently fabricated from readily available bar stock material. In addition, the holding force provided by Lattner's clamp may be inadequate under certain extreme load conditions since the wedging force is partly divided between the lateral and vertical directions viewing a cross-section of the tooth and clamp from an axial direction. Lateral clamping forces do little to aid frictional holding between the tooth and the shank under impact loads. Further, the respective surface areas of shank-tooth and tooth-clamp frictional contact in an x-z plane may be inadequate to offset certain levels of impact forces encountered in the z-direction in relation to the width of Lattner's tooth. In addition, Lattner's tooth may not adequately drive the clamp into greater clamping engagement during installation of the tooth.
Launder, on the other hand, may also suffer the same drawbacks, particularly since the surface area of frictional contact is limited to mated clamp-to-tooth curvilinear contact (which diminishes tooth-to-shank frictional holding for a given clamp-to-shank wedging force), and a relatively wide gap exists between the tooth and clamp side walls which seemingly permits lateral instability of the tooth in the x-direction during impact loads. Launder, in fact, teaches away from tooth-to-clamp side wall contact in order to attain ease in alignment, and apparently, is intended to permit separation of the clamp-tooth assembly. Above all, Launder's tooth does not self-tighten in response to axial loads applied to the tooth and cannot be positionally adjusted since there is no clearance in the z-direction between the length of the clamp receiving channel, on one hand, and the distance between the lateral ear projections and the stopwall of the tooth, on the other hand. In addition, Launder has little or no means for providing resiliency in the clamping force.
Furthermore, it is likewise desireable to provide an abrasive-resistant reversible cutting tooth of bar stock material having no perforations (bolt holes) in the body thereof, as well as, a holding clamp adapted to reversibly receive the cutting tooth in order to extend the useful life of the tooth. Such an arrangement reduces tooth breakage and machine down time. Reversible cutting teeth per se are known, such as those disclosed by U.S. Pat. No. 457,047 to Green; U.S. Pat. No. 1,058,841 to Boyd; U.S. Pat. Nos. 3,576,082 and 3,755,933 to Lowrey, and Des. Pat. No. 275,757 to Nja. However, none of these prior reversible cutting teeth are designed for use with a boltless, wedge-tightened holding clamp of the present invention which self-tightens upon the application of axial loading forces to the teeth. In addition, prior reversible teeth are prone to fatigue failure due to perforations or bolt holes generally located at their midsection. Such holes are necessary for prior reversible teeth since they are not designed for boltless connection. Unfortunately, these bolt holes yield undesirable weak points and localized stresses thereby tending to engender and propagate fatigue cracks in and about any inclusions in the body of the tooth which result in its ultimate failure during impact loads. Moreover, hardened cutting teeth having a desireable Brinell Hardness exceeding 400 are virtually impossible to machine to make perforations thus making a boltless clamping system for reversible teeth a practical necessity. These requirements suggest that hardened teeth are virtually unadaptable to prior reversible teeth systems.
In view of the foregoing, the present invention has as its objective a primary purpose to overcome the foregoing drawbacks of prior holding clamps and reversible teeth. In brief summary, the objectives of the present invention include providing a holding clamp which permits the use of bar stock material of constant cross section to form a reversible cutting tooth of a hard wear-resistant material, providing means for positionally adjusting the clamped position of the cutting tooth on a shank of an earth working digging or cutting member, providing a holding clamp of a material having a given stress-strain characteristic which provides a modulus of elasticity necessary to maintain clamp-to-shank wedging forces and for absorbing forces impacted upon the tooth during digging or cutting operations, providing a holding clamp which enables quick connecting and disconnecting of a tooth in order to reduce equipment down time, providing a holding clamp which acts to self-tighten the wedging force upon impact loads applied to the tooth during digging and/or cutting operations, providing a holding clamp and reversible tooth which requires no bolts or threaded fasteners, thereby obviating fatigue failure and adjusting difficulties due to deformations of the tooth fastening system, providing a holding clamp which is readily adapted to couple shanks and locking grooves used in the construction, agricultural and mining equipment, providing a holding clamp which provides maximum restraint against tooth movement in the x-, y- and z- directions during cutting and digging operations when engaged in clamping relation, providing a holding clamp to provide maximum force translation between clamp-to-shank wedging action and tooth-to-shank frictional holding force, providing a holding clamp having sufficient clamp-to-tooth contact force to offset extreme loading along the z-axis for holding the constant cross section portion of the tooth in the receiving channel of the clamp, and providing a boltless and reversible cutting tooth comprising a solid wear-resistant material and a corresponding holding clamp adapted to receive the reversible cutting tooth.